Because your stefans are shorter than stock darts they are not getting pushed as far down the barrel by the dart stop. Because the bolt/barrel for the LS is so short (everything else after the bolt is faux barrel) this will make a big difference.

You can't mod the clips to fix this (stefan mod won't do anything as they'll still slide forward when they reach the top, and putting rails to stop this in the top of the clip would impede bolt movement.